Electrode construction for cathoderay tubes



ELECTRODE CONSTRUCTION FOR CATHODE-RAY TUBES Filed April 19. 1954 L. W.ALVAREZ Jan. 8, 1957 2 Sheets-Sheet l EIIE IISIIHHIK IHIHI [Hill IIIHHIIHHIIHI \HIHIIHHIHH Hllll I HIIIHIHHIIIII INVENTOR. Lu/s h./fl/uaraz Jan. 8, 1957 w. ALVAREZ 2,777,083

ELECTRODE CONSTRUCTION FOR CATHODE-RAY TUBES Filed April 19; 1954 2Sheets-Sheet 2 ;z 44 34 .f 0 K a}- z/// A EIJE| 3 3/4/7} IN V EN TOR. W2 Luis M flll a/"ez EII5- E BY United tes ELECTRGDE CONSTRUCTIGN FORCATHODE- RAY TUBES Luis W. Alvarez, Berkeley, Calif., assignor toChromatic Television Laboratories, Inc, New York, N. Y., a corporationof California Application April 19, 1954, Serial No. 423,935

7 Claims. (Cl. 313-78) cent to a striped phosphor screen. A grid of thisnature may serve as one component of an electron lens system to focusthe beam electrons into a pattern of thin lines registered with thephosphor strips of the screen, and,

by the application of proper switching potentials to the linearconductors of the grid, a selective nucro deflection of the beam ontothe various phosphor areas may be brought about and hence thereproduction of a polychrome image.

One form which these linear conductors may take is that of a series ofstrips of sheet metal mounted parallel to one another in the dimensionextending across the target area and lying in planes substantiallyparallel to the paths of electrons from the gun to the phosphor coatedtar-get proper. Adjacent strips are mutually insulated from one another,and alternate strips are connected together to respective outputterminals. The elements of this strip assembly are so arranged that thestruc ture as a whole is at a substantially uniform distance from thesurface of the target area. The latter is coated with a conductive filmhaving electron permeable characteristics, so that, when suitablepotentials are applied thereto and to the strips of the electrodestructure, these elements will together constitute an electron lenswhich has a converging effect upon .the electrons of the scanning beamwhich pass between adjacent plates. This convergence may be to a linefocus on the target surface.

Alternatively, instead of plates, linear conductors as wires may beemployed. All of these linear conductors are intended to lie in .asingle plane close to the sur face of the target electrode.

The above effect will be more clearly understood when the action of theelectrostatic field in the region of the conductors on an electronpassing between adjacent conductors is considered. The lines of forcewhich comprise this electrostatic field set upon the electrons in thescanning beams in such a manner that any particular electron passingthrough the space between two adjacent strand conductors (unless itpasses through the exact center of the space between these conductorsand normal to the plane thereof) is directed away from the nearestconductor by the lateral component of this electrostatic field.Expressed ditferently, an electron passing perpendicularly through theexact center of the space between adjacent conductors will cross or cutnone of the lines of force, and therefore will hold to its originalp-ath. An electron passing very close to either conductor Patented Jan.8, 1957 will cut a major portion of the field lines term 'mating on thatconductor, and therefore will be repelled from the latter by arelatively large lateral force. It may thus be said that all of theelectrons in the scanning beam which pass between any two adjacentconductors are subjected to lateral forces which are at leastapproximately proportional to their distance from the axis of theindividual lens defined by the conductors in question, so that there isa resultant convergence of the beam electrons toward a single line uponthe phosphor-coated target surface.

As brought out above, adjacent conductors of the electrode assembly aremutually insulated and alternate strips or conductors are connectedtogether. If now a difference of potential is applied between these twosets of conductors, a deflection field is created such that all of theelectrons in the beam passing through the interspace between theconductors will be given equal accelerations away from the conductorwhich is negative toward the one which is positive. The result is ashifting of focus toward whichever of the conductors happens to bepositive at the moment. In adjacent elementary lenses, therefore, thedeflection occurs in opposite directions.

In the case of deflection of the beam at a field-sequential rate, thecolon-control voltage used will preferably be of substantiallyrectangular wave form of a frequency equal to one-third the fieldfrequency, the wave form having a positive potential for the firstone-third of the cycle, zero for the next onethird, and negative for thelast one-third of the cycle. With a line-sequential systern, the waveform might be substantially the same but at one-third line instead ofone-third field frequency. The dot-sequential system, or one in whichcolors are displayed at socalled element frequency, could still use thesame wave form at a corresponding higher frequency, or this wave formcould be that of a sine WIZJVS which would display green twice per cyclefora short period, and red and blue once per cycle for a longer period.As a still further example, this sine wave could be broken up intodisplay periods spaced 60 electrical degrees apart.

When the phosphor-coated target is covered with an electron-permeablelayer of conductive material, and when this electron-permeable layer hasa potential applied thereto which is considerably higher than theaverage, or mean, potential of the deflecting electrode, then verylittle power will be required to cause a deflection of the cathode-raybeam back-and-forth between various colored phosphor areas of the screenin the manner above described. It will also be recognized that thefrequency of color change has a very material effect upon the powerrequirements, the latter being very much higher for color changeproduced at so-called element frequency than it is for either lineorfield-sequential color change.

In any grid structure constructed in accordance with the above, it isfundamental that the lateral velocity imparted to electrons passingbetween adjacent conductors, is proportional to the number'of lines offorce they cross or out. It is also fundamental that the number of linesof force produced in the space between adjacent conductors isproportional to the high frequency alternating current which charges anddischarges the conductors to create the electronic field. Since thepower requirement of the structure are directly proportional to thevoltage multiplied by this charging current divided by the circuitefficiency factor Q, it will be seen that a reduction in the requiredpower may be brought about if some way can be found of opera-ting thetube with a lower voltage on the grid conductors without decreasingdeflection field strength. This the present invention is designed toaccomplish.

In accordance with a principal feature of this disclosure .thapwe .tequrement in .aeathoderay tube of the nature described above are materiallyreduced by lowering the voltage applied to the strand conductors .o hegri s ructure i 'a rd rl t t-prod a micr ;d qn of h sca in :be m- -.I am.u h .1 th PP varies in direct :preportion to,-the-,;applied-v.oltage,-.and inasmuch,as'theqlatter isinverselyproportionaito the capacity between;adjaeent. -elementsof t-he;., grid,this, capacity :is raised -.by;ut,-i lizing.1w sets-of: lineanconductors instead :of one set; lying-onebehind; the other along-the e to m t t the nhesp en arg r Qne. object of the present ,---invention,therefore, is to -provide a grid structure of the,- above natureor;imagereproducing cathode-ray tubes designed to,reeonstitute images in..p olychrome.

,A further: object of;thepresent inventionis to reduce the powerrequired for .micro-defleetion in .a cathoderay tube of-the,.above;type.

A.. still further. objecteof the;p res,ent invention is -:to Pr v d a rath -ray t be d s gned t rspo y hr me image vreproduction andincorporating a grid structure positioned adjacent toa stripedphosphoriscreen, in which the powerrequired by.this--grid structureformicro-de- -ilection of the cathode-ray beam-.is materiallymeducedover structures previously (employed.

Otherobjects,,andadvantages of the presentinvention will be apparentfrom the following description and from .therdrawings, in which:

Figure I is asemi-diagrammaticview of a cathoderay.tube showing'incrossrscct-ion a color;,gridstructure in accordance @with the presentvinvention;

Figure'2 is a plan .viewvofrthe. color grid structure-of Fig. 1; as-scenfromthe, electron, gun end of;the.-cathoderay t be;

Figure v3 isia detailedview eta-portion of-Fig. 2;

,Figure 4-is,a perspective'view ;of Fig.3, showing-in addition onemanner of (securing-the base plateassembly ,to; the color grid unit;

figure 5 .is;a;perspectiveview of aport-ion. of --Fig. 3, ,showing infurther detail the mannerinxwhich thfiztWO .sets of ,grid conductors arepositioned by .the grooved side members;

Figure. 6 is an end- ,-vi ew of one of the side -members of Figs. 3, 4,and 5, yShOWirigI-h manner in nwhich -arr-ivingwan.d;dep arting -wires\o f av single turn are eaused' ,tog'bepositioned one; above theother bymeans ofigrooves ;cut into thesurface of the :side member; and

Figure .7 ,isa;plan-view-of a portion of the target. area -of ,Fig. 2,showing one preferred relationship between the 1 grid conductors" andphosphor .strips.

Referring now.to;the-;drawing, there isshown in Fig. 1 a cathode-raytube certain ;-parts of which .are :coniventional. For example, in the:neck end of :the en- \velope it) there is an indirectlyrheated cathode1,2 which act vas a sour e of ele ron f0r .dev 1 pment ,into a sc n nbeam. the l r 111' indic e rseh mtica ly vih rac At ia en tton na-rtilly;. u ounding :the thod 1 2 1 cen ro ..-g-tt elre ele r e 161 .ahlyapertured 1, to permit @the passage ;of ;electrons which aresubsequently for-med into the .beam :14. Ihe c n- -trol grid .16functions in ,the usual manner zto -m0d u- .late the emittedstreamofaelectrons in accordance with tl1e potential applied ;theretorelativeztolthe eathode 12. .Alsoin the-.neck-;end\of the:tubeithereiisprovided agrid #2 or first anode tidentified by :Ecferencemumeral .118).to which .suitable potentials l-may vb .flhp ied $80 as to -result inaninitial acceleration-of the;electrons ernitted zfrom thercathode d2.-Adjacentitoithe grid:,#;3 there is ;-p,os-itioned a grid or secondanode ,Qreference numeral 20) for supplying an ,additional accelerationto theelectron.

:D,fi g w t t mnr sin a horiz Pa. r s22 .andva vertical pair-. ZZQ- areprovided for ;tl 1 e usual scanning purposes. Obviously, the termshorizontal ;and

--fvertic-al .are used herein in ;a descriptive. :tsen-se :only.

'4 Thus, the electron beam 14 is caused to scan a phosphor-coatedtarget, or base plate, 26 to develop light which is visible through theend wall 28 of the envelope 10.

Best shown in Fig. 2 is a substantially rectangular frame 30 adapted tofit within the envelope of the cathode-ray tube 10. This frame 30 ismade up of a pair of oppositely-disposed -L-sh aped channel members 32,which form two sidesof theframe, and a pair of grooved .side, members34.which; form the remainingtwo sides, thus defining a centralwindow,.a-rea. 1'Ihe'.,L-shaped members 32 are respectively securedJtothe-.side-anembers 34 by rivets ,36, :one of Which is shownin each ofFigs. 4 and 5. Each side member34'is of generally flat configuration,and maybe fabricated for example, from .062" thick type 430 stainlesssteel sheet bent double as indicated in the drawing. However, theparticular manner of fabricating the frame-30 formsno part of ,the;present invention, and anygindication that it. maybe formed by bendingand rivetingroperationsis;merelyrfor the, purpose ,of. explanation.

.Theframe 30 is provided .at :each:v corner .withsa lug vor.tab,38-vvhich is .shown in;Fig..2.;ashavin g. a contour generally similar to theinternal .periphery..of .the-envelope .10. ,In thecaseofwametal-envelopelO, small angles 40 may be welded to the inside surface.ofthe envelope EllizPOSitiOHS .where.it .is desiredtoattachthe lugs 38..T helugsare joined to the .angles bymeans of. rivetsAZavhich preferablyassthmughMceramic. bushings .(not shown) which areprovided .withinsulating di-scs.on eachend to isolate ,electricallytthe frame 30 fromtheenvelope 10. Other meansof attachment may be employed, especially.when ,glassinstead Ofmetal en- ,velopes are used. l-Iowever, .these.constructional featnres per seformno-partof the. present invention,.and

furtherrnoreareof the samegeneralnature ,asalready' in use in the art,so that no further details in regard thereto vwill beset forth herein.

A. first continuous. filamentaryconductor. (such as #302.stainless-steel of.6 milthickness) is wound around theoppositely-disposed frame ,side members 34 in coil-like fashion so as toformtwohsets .of .strands. One such set of strands (indieatedin thedrawingby.the reference numeral 44) .is.comp.osed of thoseWhich1passalong the upper surface. of each grooved, side member 34 .(as.best showniniFig. 5) .and the. o.t,her=set.of strands :(idmtified as.46) is.c0mp0sed;of those passing along the under surface;of the sidemember. .It will be apparent from aconsideration of the drawings, ,andespecially Figs. 3, -.4 and 5,.thatthese two sets of strandconductors-lie in separateplanes one above the other, the distance be-,tweenthe planes being determined by the thickness of vthe framemember.3f4.

The .above .operation, which may be termed the first,or.initial,.winding, is so carried out that the spacing'be- .tweenadjacent turns .is substantially twice the spacing desired betweenadjacent conductors tof the finished, grid assembly. Eurthermore, ,sinceeachiturn of theifir'st winding operation consists of an arriving,.oriuppenstrand .44 ,and a .departing, or .lower, :strand '46, these-twostrands whichconstitute-a singleturn are intended .to lie in a :planewhich .is .nominally .vertical, .or normal, .torthe surface ofthe ,baseplate .26, but at=the same.,time.departs from this normal state byvarying .amounts fromcne --section-of-the finished gridassembly totheother depend- -ingtupon-the angle of .lIlGidGHCBgOf the. electronbeam. as it arrives at such po-int from the electrongunend:ofithe,cathode-ray :tube. Expressed differently, theaplane .in which these-,two strand conductors of a ,single turn; lie issubstantially;paralleltothe path ofascanning-heamelectron the trajectoryof'whiehilies inaor adjacent lZO'athiS pla e.,Hence,,in1a;general-.sense, itimay besaid that this :plane (whi hincludes the 1two-,strand. conductors making ;up :a; single turn ofthersO-Qfllldififst (winding) als o,in-

:cludes'the gcenter .of deflection pf thetcathodeqray beam.

In order to insure that each of the strand conductors 44 and 46 whichtogether constitute a single turn of the first winding lie in such aplane, grooves are cut into the outer edge of one of the side members34, with the direction of such grooves being nominally vertical ornormal to the plane of the finished grid, but at the same time deviatingfrom this normal condition by an amount necessary to take into accountthe angle at which the cathoderay scanning beam arrives at the plane ofthe grid assembly. Such grooves are generally indicated by the referencenumeral 43 in Fig. 4, and are so cut into the side member 34 that thefirst winding operation described above results in the continuousfilamentary conductor being received in these grooves to thus establishthe position of the strands as they cross the open, or window areadefined by the frame members. It is intended that the parallel conditionof the wires constituting each turn be maintained across the entirewindow area of the cathode-ray tube.

Means must also be provided for causing the wire to be shiftedlaterally'to a new position following the completion of any particularturn and prior to the commencement of a succeeding turn, so that duringthe latter winding the two strand conductors 44 and 46 thereof will alsobe substantially parallel to one another and lie directly one above theother as seen by an electron passing adjacent thereto. To produce thisoffset condition of successive turns of the so-called first windingoperation, the remaining one of the two side members 34 has grooves cutinto its outer edge which are not substantially normal to the plane ofthe grid assembly (as are the grooves of the first-mentioned member) butinstead are caused to have the angular relationship best illustrated inFig. 6 of the drawings.

As shown in this figure, the upper, or arriving, strand conductors 44which are formed by the first winding operation (or by wire #1 asindicated in this figure) arrive along the upper surface of the sidemember 34 in the position shown. However, in passing over the outer edgeof this side member, they fall within grooves which are cut angularly asindicated in the drawing. By the time the wire reaches the lower, orunder, surface of the side member, it is offset to the position 46 showntherein. This position 46 bears such a relationship to the position 44that (considered in a plane normal to the plane of the frame member) itis shifted laterally by substantially twice the distance desired betweenadjacent turns of the finished grid assembly.

Following the first winding operation set forth above, a second windingoperation is carried out in an exactly similar manner except that (asbest shown in Fig. 6) wire #2 begins at a point midway between twoadjacent turns of wire #1. This second winding operation produces twofurther sets of conductors lying intermediate the conductors 44 and 46,and hence these two second sets of conductors are given the designations44a and 46a (see Figs. 4, 5 and 6). Each turn of the second windingoperation forms two strand conductors 44a and 46a lying in anessentially vertical plane in the same manner as two correspondingconductors 44 and 46 formed by the first winding operation. Thus, thefinished grid assembly, as shown in the drawings, consists of two setsof strands lying intermediate each other (insofar as the spacing betweenadjacent turns is concerned) and with each turn of each windingoperation producing two conductors which lie one above the other as theyare viewed by an electron of the scanning beam 14. Consequently, such anelectron passing between two adjacent upper strand conductors 44 and 44awill likewise pass between two lower strands 46 and 46a. This will beclear from a consideration of Figs. 3 and 4 of the drawings.

Since different potentials are intended to be applied to the two sets ofstrand conductors respectively formed by the two winding operations (or,in other words, wires #1 and #2 as indicated in Fig. 6) means areprovided for insulating these two sets of conductors both from eachother and from the electrically-conductive side members 34 which formpart of the frame 30. One preferred means of accomplishing this resultis by coating the entire frame 30 (or, alternatively, coating only thegrooved side members 34) with a suitable insulating substance. Thiscoating may be applied by spraying the frame with thermo-setting enamelor liquid porcelain, for example, prior to the above-mentioned windingoperations. This will result in a thin film of insulation being formedover that portion of the surface of the frame contacted by the strandconductors of the grid assembly.

The backing area, or base plate, 26 carries on one of its surfaces aseries of phosphor strips laid down in a manner such as will bedescribed in connection with Fig. 7. That is, the sequence of thesephosphor strips may be, for example, red, green, blue, green, red,green, etc. For satisfactory operation of the tube being described, itis necessary that each of the strand conductors be properly positionedwith respect to these phosphor strips. That is, wires are associatedwith each red and blue strip but none with the green.

The base plate 26 is mounted in a pair of L-shaped support members 48,one of which is shown in each of Figs. 3 and 4. The plate 26 is cradledin these support members in the manner shown, the latter beingpreferably composed of the same material as the frame sections 32 and34.

There have now been described two units, or sub-assemblies, one of whichmay be designated as the grid wire sub-assembly, as shown in Fig. 5, forexample, and the remaining one constituting the base plate sub-assembly,which includes the phosphor-coated plate 26 and the two support members48. These two sub-assemblies are now brought into position as best shownin Fig. 4, and, in this position, the two units are secured together bymeans of the angles 50 (one of which is shown in Fig. 4). The rivet 36,which joins one of the L-shaped channel members 32 to one of the groovedside members 34, may also pass through this angle 50, as best shown inFig. 4, while another rivet 52 secures the angle 50 to the base platesupport member 48. Obviously, four such securing means are employed, oneon each corner of the frame 30.

The relative position of the conducting strands, or grid wires, andthered, blue and green phosphor strips which are applied to that surface ofthe base plate 26 impacted by the electron scanning beam 14, is shown inFig. 7. Although the particular arrangement of the phosphor strips formsno part of the present invention, nevertheless a desirable'pattern hasbeen found to consist of repeating groups of strips in the order red,green, blue, green, red, green, etc. The strip widths are chosen inaccordance with tube design so as to provide electro-optical rather thanphysical relationships between the grid wires and the phosphor strips.Each adjacent pair of grid wires accordingly is designed to subtend (inan electro-optical sense) a portion of the target electrode surfacewhich includes phosphor areas of each of the component colors. Generallyspeaking, however, it may be said that the distance between adjacentgrid wires is substantially equal in one dimension to a single elementalarea of the image to be resolved by the cathode-ray tube.

It will now be appreciated that an electron of the scanning beam 14arriving at the grid wire assembly from the main deflecting area of thecathode-ray tube 10 will pass first through one of the apertures formedby a strand conductor 44 and an adjacent strand conductor 44a. As such,the electron will be subjected to a micro-deflection in a sidewise, ortransverse, direction the magnitude of which depends upon the potentialsapplied to these conductors 44 and 44a. Expressed differently, there isan electric field established between these conductors and theelectron-in question will be subjected to a'- la'teral'deflectiomdepent'iing upon the number of lines off-force-of thiselectrostatic-field "cut by the electron during its passage between thetwo strand conductors. After passing'through'this area, the electroncontinues toward the base plate 2'6, and passes through asecondele'ct'ric field developed 'betweentwo lower conductors 46 and46a. In passing through this se'cond electrostatic field, the electroncuts a further number of lines of force,and, hence, is subjected to- -afurther transverse o'r micro defl'ec'tio'n depending again u'pon thenumber of field lines cut thereby. These two 'micro deflection' forceswhen added together, produce: a total deflection of the electronwhich'is greater than: that produced by'either. field alone.

Instead of producing a greater overall deflectiont ofthe electron beam,it will be recognizedthat a deflection may be obtained whichise'qualtorthatproduced by the electro static field developed between al single'set'of conductors through-the expedient of causing each of the twofields to produce approximately half the total desired deflection; Thevoltage required for producing such a total deflection by these'twoindividual fieldsacting in sequence-may be only half of the voltagerequired to produce the same deflection by a single field, inasmuch asthe capacity factor ofthe grid assembly hasbeen doubled.

A still further advantage to be realized by employing the concept setforth in the present application is that the tendency of theindividualstrand conductors of the grid to vibrate due to rapid changesin the value of the color switching potentials is very materiallyreduced as the magnitude of these 'deflection'potentials is lowered. Theimportance of inhibiting grid wire vibration is brought out in acopending United States patent application. of Howard R. Patterson,Serial No. 364,778, filed June 29, 19.53, and assigned to the sameassignee as the present application. In this Patterson application, itis brought out that unrestricted vibration of the grid wires, in manycases, produces such severe color contamination in. the reproduced imageas to make the latter commercially unacceptable. By producing the samedegree of microdeflection of the cathode-ray beam with reduceddeflection potentials, as is accomplished by use of the conceptdisclosedherein, the vibrational elfects of the grid assembly are muchless severe, and in some cases it may even be possible to omit thevarious damping devices which previously had been mandatory in grid wireconstruction of the present type.

A still further benefit obtained from the use of a grid assemblyconstructedzin accordance with the present invention is'that stars orrandom spots of intense illumir nation developed on the phosphor-coatedtarget, are reduced both in number and'severity due to the decreasedelectron emission from the grid wireswhen lower deflecting voltages areemployed. Still further, a grid structure wound in continuous fashion(as in the one set forth herein) doesnot possess many ofthe propertiesinherent in gridstructures fabricated by back-and-forth wind ingtechniques, such-as-the problem of the wires adhering to the hooksaround which they pass.v

In summary, therefore, it may be said that one of the principaladvantages of the present invention resides in a lowering of the powerrequirementsfor micro-deflection of a cathode-ray beam, in a tube of thenature described above, by causing the scanning beam electrons to passsequentially through two-electrostatic fields each of which produces alateral deflection of the cathode-ray beam for color-changing purposes.The two fields acting together may crcatea condition in which anelectron passing therethrough cuts double the number of lines of forcewhich it would'cut in passage through-one of the .two field's alone.Consequently, its lateral deflection may be double that of a singlefield. For thesameamount of deflection, each of the two fields ofthis'di sclosure' maybe so developed that the number of linesof' forceout by an electron is substa'ntiallyequalto thatof'a single grid. This)requires but half as r'nuch voltage on the conductors and consequentlyles's deflecting power.

Having thus-described the invention, what is claimed is:

l-. =Ina grid structure designed for incorporation into'a cathode-raytube having a phosphor-coated target electrode on'which images arereconstituted in a plurality of colors: the combination of a framehaving two pairsof oppositely dispos'ed members together defining aWindow area thereb'etween, one member of one of the said pairsbeing'provided with aseries of parallel grooves onits outer edge,thedirection of said grooves being essentially normal to the :plane ofsaid frame, the other member of saidone pair also being provided with aseries of parallelgrooves on its outer edge, the direction of saidlast-men'- tionedJgrooves being other than essentially normal to theplane'of said frame; a. first continuous conductor wound in coil-likefashion around said frame and electrically insulatedtherefromwithsuccessive turns of said'co'il lying within alternate grooves in each ofsaid one pair of frame members; and a second continuous conductor alsowound in coil-like fashionaround said frame and electricallyinsulatedtherefrom with successive turnsof said coil lying within thealternate grooves in each of said one pair of frame members not occupiedby said first conductor, thereby to formtwosets of interleaved parallelstrands across the Window of said frame respectively lying in planeswhich are separate yetparallel to one another, with each completeturn ofboth saidfirst conductor and said second conductor consisting of twostrands defining a plane which is substantially parallel to thetrajectory of an electron developed Within said cathode-ray tube anddirected to that area of the said target electrode proximate to the saidtwo strands.

2 In a grid structure designedfor incorporation into a cathode-ray tubein which an electron scanning beam is developed and then deflected so asto scan a phosphorcoated-target thereby to reconstitute images in aplurality of colors, the combination of a grid structure positionedadjacent to said target and in the path of the said scanning beam,- saidgrid structure including a pair'of continuous electrical conductorswoundin coil-like fashion so that each turn of each'conductor consists of twostrands lying in a plane substantially parallel to the trajectory of anelectron developed by said cathode-ray tube and direct'ed t'othat'p'ortion of said target adjacent said' two strands, such that thelatter are passed sequentially by said electron in its journey to saidtarget, and means for electrically insulating one of said pair ofconductors from the other so that diiferent electrical potentialsmay'b'e'applied thereto while maintaining allp'ortions of eachindividual conductor in a substantially unipotential condition.

3. In a grid structure designed for incorporation into acathode-'raytube'having a phosphor-coated target electrode which theelectron scanning beam of said tube is caused to impinge thereby toreconstitute images in a plurality of colors, the-combination of asubstantially'rec tangular frame; a first continuous conductor wound inessentially coil-like fashion around oppositely-disposed portions ofsaid frame so'that each turn of saidcoil-like winding consists oftwo'st'rands each of which lies substantially" equidistantly throughoutits length from the phosphor-coated surface of said target electrode;and with the two said strands defining a plane essentially parallel-'toth'e' path of' an electronof said scanning beam passing adjacent to saidstrands-toward said targetelee trode, whereby the. electron in followingthis path" will pass'th'e' two said-strands in sequence, a secondcontinuous conductor also wound in essentially coil-like fashionaround'said frame sothatthetu'rns formed by said-second conductor areinterleaved with the turnsfo'rmed by said first conductorand areelectrically insulated therefrom, eaclilturnformed by saidsecondconducto'r also consisting of two strands each of which liessubstantially equi distantly-'throughoiit' its length fromthephosphor-coated 9 surface of said target electrode, and with the twolastmentioned strands also defining a plane essentially parallel to thepath of an electron of said scanning beam passing adjacent to saidstrands toward said target electrode such that the electron in followingthis path will pass by the two said strands in sequence.

4. In a cathode-ray tube for color television, a grid structure adaptedfor positioning substantially adjacent to a target upon which is acoating of a plurality of different phosphors arranged in stripformation in a repeating cycle and which strips are adapted to becomeluminous in different colors under electron beam impact, which comprisesa first plurality of generally uniformly spaced linear conductorssupported in substantially parallel relationship to each other along asurface adapted to be located adjacent to the target and within thecathode-ray tube to extend within the electron beam path to the targetsubstantially parallel to the strips of the target, a second pluralityof linear conductors extending parallel to the linear conductors of thefirst set and spaced from each other by substantially the spacings ofthe con ductors of the first set and uniformly spaced from theconductors of the first set, the linear conductors of the second setbeing adjacent to those of the first set and adapted to be held closerto the electron beam source than the linear conductors of the first set,means to connect electrically alternate linear conductors of each set tomaintain the connected conductors at like potential and so as to connectadjacent conductors to permit the application of different relativepotentials thereto, and means to connect the conductors of the two setselectrically in parallel.

5. A grid structure for a cathode-ray tube comprising a pair ofparallelly positioned support elements spaced by substantially onedimension of a raster to be traced upon the tube target, a plurality ofparallelly tautly strung conductors stretched between the supports, onepart of the conductors being stretched between the supports to lie atone side thereof in a surface defined by the support and the other partof the conductors being stretched between the supports to lie at theother side thereof with each conductor of each set equally spaced fromthe space-related conductor of the other set, means to connectelectrically alternate linear conductors of each set to maintain theconnected conductors at like potential and so as to connect adjacentconductors to permit the application of different relative potentialsthereto, and means to connect the conductors of the two setselectrically in parallel.

6. In color television apparatus, a grid structure adapted forpositioning substantially adjacent to a target having thereon coatingsof material adapted to luminesce in selected color light under electronbeam impact according to a repeating pattern of strips arranged in acycle of an additive color series which comprises a pair of supportsseparated from each other by a distance at least as great as onedimension of a raster to be traced in the target, a first conductor 10strung back and forth between and around each of the supports and in acontinuous strand pattern extending lengthwise of the support with eachadjacent strand substantially uniformly spaced and each adapted toextend parallel to the target strips and of which the portion spanningthe distance between the supports on one side thereof is uniformlyspaced from the portion spanning the distance between the supports onthe other side thereof, a second conductor similarly strung between thesupports with each conducting strand spanning the distance between thesupports being positioned intermediate a corresponding strand of thefirst conductor, means electrically to insulate the conductors of eachset and means to apply potentials to each. conductor so that at eitherside of the supports a grid structure is provided wherein alternateconductors are maintained at like potential and adjacent conductors maybe maintained at relative potentials in accordance with the suppliedpotentials.

7. In a cathode-ray tube for color television, having a target formed asa coating of a plurality of difierent light producing phosphors arrangedin strip formation in a repeating cycle and adapted to become luminousunder electron beam impact to develop light in colors additive toproduce white light, a grid structure adapted for positioning adjacentto the target for color switching control which comprises a firstplurality of generally uniformly spaced linear conductors in parallelrelationship to each other supported along a surface adapted to locateadjacent to the target and in the cathode-ray beam path to the targetwith. the conductors extending parallel to the strips of the target, asecond plurality of uniformly spaced linear conductors also in parallelrelationship to each other and extending parallel to the linearconductors of the first set and spaced from each other by substantiallythe spacings of the conductors of the first set and uniformly spacedfrom the conductors of the first set, the linear conductors of thesecond set being located adjacent to those of the first set and in suchrelation thereto as to be closer to the electron beam source and moreremote from the target than the linear conductors of the first set,means to connect electrically alternate linear conductors of each set tomaintain the connected conductors at like potential and so as to connectadjacent conductors to permit the application of different relativepotentials thereto and means to connect the conductors of the two setselectrically in parallel.

References Cited in the file of this patent UNITED STATES PATENTS Re.23,672 Okolicsanyi June 23, 1953 1,565,708 Bullimore Dec. 15, 19251,980,341 Kayko et a1. Nov. 13, 1934 2,067,825 Bullimore Ian. 12, 19372,660,684 Parker Nov. 24, 1953

